/* this file is a part of amp software, (C) tomislav uzelac 1996,1997
 */

/* getdata.c  scalefactor & huffman data extraction
 *
 * Created by: tomislav uzelac  Apr 1996
 * Last modified by: tomislav uzelac  Feb 27 1997
 */
#include "amp.h"
#include "audio.h"
#include "getbits.h"
#include "huffman.h"

#define		GETDATA
#include "getdata.h"

/* layer3 scalefactor decoding. should we check for the number
 * of bits read, just in case?
 */
int decode_scalefactors(struct SIDE_INFO *info,struct AUDIO_HEADER *header,int gr,int ch)
{
    int sfb,window;
    int slen1,slen2;
    int i1,i2,i=0;
    int j,k;
    if (header->ID==1) {
        /* this is MPEG-1 scalefactors format, quite different than
         * the MPEG-2 format.
         */
        slen1=t_slen1[info->scalefac_compress[gr][ch]];
        slen2=t_slen2[info->scalefac_compress[gr][ch]];
        i1=3*slen1;
        i2=3*slen2;

        if (info->window_switching_flag[gr][ch] && info->block_type[gr][ch]==2) {
            if (info->mixed_block_flag[gr][ch]) {
                for (sfb=0;sfb<8;sfb++) {
                    scalefac_l[gr][ch][sfb]=getbits(slen1);
                    i+=slen1;
                }
                for (sfb=3;sfb<6;sfb++) {
                    for (window=0;window<3;window++)
                        scalefac_s[gr][ch][sfb][window]=getbits(slen1);
                    i+=i1;
                }
                for (;sfb<12;sfb++) {
                    for (window=0;window<3;window++)
                        scalefac_s[gr][ch][sfb][window]=getbits(slen2);
                    i+=i2;
                }
            } else { /* !mixed_block_flag */
                for (sfb=0;sfb<6;sfb++) {
                    for (window=0;window<3;window++)
                        scalefac_s[gr][ch][sfb][window]=getbits(slen1);
                    i+=i1;
                }
                for (;sfb<12;sfb++) {
                    for (window=0;window<3;window++)
                        scalefac_s[gr][ch][sfb][window]=getbits(slen2);
                    i+=i2;
                }
            }
            for (window=0;window<3;window++)
                scalefac_s[gr][ch][12][window]=0;
        } else { /* block_type!=2 */
            if ( !info->scfsi[ch][0] || !gr )
                for (sfb=0;sfb<6;sfb++) {
                    scalefac_l[gr][ch][sfb]=getbits(slen1);
                    i+=slen1;
                }
            else for (sfb=0;sfb<6;sfb++) {
                scalefac_l[1][ch][sfb]=scalefac_l[0][ch][sfb];
            }
            if ( !info->scfsi[ch][1] || !gr )
                for (sfb=6;sfb<11;sfb++) {
                    scalefac_l[gr][ch][sfb]=getbits(slen1);
                    i+=slen1;
                }
            else for (sfb=6;sfb<11;sfb++) {
                scalefac_l[1][ch][sfb]=scalefac_l[0][ch][sfb];
            }
            if ( !info->scfsi[ch][2] || !gr )
                for (sfb=11;sfb<16;sfb++) {
                    scalefac_l[gr][ch][sfb]=getbits(slen2);
                    i+=slen2;
                }
            else for (sfb=11;sfb<16;sfb++) {
                scalefac_l[1][ch][sfb]=scalefac_l[0][ch][sfb];
            }
            if ( !info->scfsi[ch][3] || !gr )
                for (sfb=16;sfb<21;sfb++) {
                    scalefac_l[gr][ch][sfb]=getbits(slen2);
                    i+=slen2;
                }
            else for (sfb=16;sfb<21;sfb++) {
                scalefac_l[1][ch][sfb]=scalefac_l[0][ch][sfb];
            }
            scalefac_l[gr][ch][21]=0;
        }
    } else { /* ID==0 */
        int index=0,index2,spooky_index;
        int slen[5],nr_of_sfb[5]; /* actually, there's four of each, not five, labelled 1 through 4, but
        * what's a word of storage compared to one's sanity. so [0] is irellevant.
        */

        /* ok, so we got 3 indexes.
         * spooky_index - indicates whether we use the normal set of slen eqs and nr_of_sfb tables
         *                or the one for the right channel of intensity stereo coded frame
         * index        - corresponds to the value of scalefac_compress, as listed in the standard
         * index2	- 0 for long blocks, 1 for short wo/ mixed_block_flag, 2 for short with it
         */
        if ( (header->mode_extension==1 || header->mode_extension==3) && ch==1) { /* right ch... */
            int int_scalefac_compress=info->scalefac_compress[0][ch]>>1;
            intensity_scale=info->scalefac_compress[0][1]&1;
            spooky_index=1;
            if (int_scalefac_compress < 180) {
                slen[1]=int_scalefac_compress/36;
                slen[2]=(int_scalefac_compress%36)/6;
                slen[3]=(int_scalefac_compress%36)%6;
                slen[4]=0;
                info->preflag[0][ch]=0;
                index=0;
            }
            if ( 180 <= int_scalefac_compress && int_scalefac_compress < 244) {
                slen[1]=((int_scalefac_compress-180)%64)>>4;
                slen[2]=((int_scalefac_compress-180)%16)>>2;
                slen[3]=(int_scalefac_compress-180)%4;
                slen[4]=0;
                info->preflag[0][ch]=0;
                index=1;
            }
            if ( 244 <= int_scalefac_compress && int_scalefac_compress < 255) {
                slen[1]=(int_scalefac_compress-244)/3;
                slen[2]=(int_scalefac_compress-244)%3;
                slen[3]=0;
                slen[4]=0;
                info->preflag[0][ch]=0;
                index=2;
            }
        } else { /* the usual */
            spooky_index=0;
            if (info->scalefac_compress[0][ch] < 400) {
                slen[1]=(info->scalefac_compress[0][ch]>>4)/5;
                slen[2]=(info->scalefac_compress[0][ch]>>4)%5;
                slen[3]=(info->scalefac_compress[0][ch]%16)>>2;
                slen[4]=info->scalefac_compress[0][ch]%4;
                info->preflag[0][ch]=0;
                index=0;
            }
            if (info->scalefac_compress[0][ch] >= 400 && info->scalefac_compress[0][ch] < 500) {
                slen[1]=((info->scalefac_compress[0][ch]-400)>>2)/5;
                slen[2]=((info->scalefac_compress[0][ch]-400)>>2)%5;
                slen[3]=(info->scalefac_compress[0][ch]-400)%4;
                slen[4]=0;
                info->preflag[0][ch]=0;
                index=1;
            }
            if (info->scalefac_compress[0][ch] >= 500 && info->scalefac_compress[0][ch] < 512) {
                slen[1]=(info->scalefac_compress[0][ch]-500)/3;
                slen[2]=(info->scalefac_compress[0][ch]-500)%3;
                slen[3]=0;
                slen[4]=0;
                info->preflag[0][ch]=1;
                index=2;
            }
        }

        if (info->window_switching_flag[0][ch] && info->block_type[0][ch]==2)
            if (info->mixed_block_flag[0][ch]) index2=2;
            else index2=1;
        else index2=0;

        for (j=1;j<=4;j++) nr_of_sfb[j]=spooky_table[spooky_index][index][index2][j-1];

        /* now we'll do some actual scalefactor extraction, and a little more.
         * for each scalefactor band we'll set the value of is_max to indicate
         * illegal is_pos, since with MPEG2 it's not 'hardcoded' to 7.
         */
        if (!info->window_switching_flag[0][ch] || (info->window_switching_flag[0][ch] && info->block_type[0][ch]!=2)) {
            sfb=0;
            for (j=1;j<=4;j++)
                for (k=0;k<nr_of_sfb[j];k++) {
                    scalefac_l[0][ch][sfb]=getbits(slen[j]);
                    i+=slen[j];
                    if (ch) is_max[sfb]=(1<<slen[j])-1;
                    sfb++;
                }
        } else if (info->block_type[0][ch]==2)
            if (!info->mixed_block_flag[0][ch]) {
                sfb=0;
                for (j=1;j<=4;j++)
                    for (k=0;k<nr_of_sfb[j];k+=3) {
                        /* we assume here that nr_of_sfb is divisible by 3. it is.
                         */
                        scalefac_s[0][ch][sfb][0]=getbits(slen[j]);
                        scalefac_s[0][ch][sfb][1]=getbits(slen[j]);
                        scalefac_s[0][ch][sfb][2]=getbits(slen[j]);
                        i+=3*slen[j];
                        if (ch) is_max[sfb+6]=(1<<slen[j])-1;
                        sfb++;
                    }
            } else {
                /* what we do here is:
                 * 1. assume that for every fs, the two lowest subbands are equal to the
                 *    six lowest scalefactor bands for long blocks/MPEG2. they are.
                 * 2. assume that for every fs, the two lowest subbands are equal to the
                 *    three lowest scalefactor bands for short blocks. they are.
                 */
                sfb=0;
                for (k=0;k<6;k++) {
                    scalefac_l[0][ch][sfb]=getbits(slen[1]);
                    i+=slen[j];
                    if (ch) is_max[sfb]=(1<<slen[1])-1;
                    sfb++;
                }
                nr_of_sfb[1]-=6;
                sfb=3;
                for (j=1;j<=4;j++)
                    for (k=0;k<nr_of_sfb[j];k+=3) {
                        scalefac_s[0][ch][sfb][0]=getbits(slen[j]);
                        scalefac_s[0][ch][sfb][1]=getbits(slen[j]);
                        scalefac_s[0][ch][sfb][2]=getbits(slen[j]);
                        i+=3*slen[j];
                        if (ch) is_max[sfb+6]=(1<<slen[j])-1;
                        sfb++;
                    }
            }
    }
    return i;
}
